1. Field of the Invention
The present invention relates to a transflective liquid crystal display panel and method of making the same, and more particularly, to a transflective liquid crystal display panel with high aperture ratio, and a method of making the same with simplified process steps.
2. Description of the Prior Art
Liquid crystal display (LCD), based on different light sources, may be classified into three types including: transmission type, reflection type and transflective type. The transmission LCD requires a back light module, which is disposed behind the LCD panel and able to generate light beams passing the LCD panel so that the user can see images in front of the transmission LCD. The reflective LCD uses ambient light as its light source, and requires forming reflection electrodes in each pixel. The ambient light enters the reflective LCD from its front side (observation screen) and is reflected by the reflection electrodes so that the user can see images from the front side of the reflective LCD. The transflective LCD includes both transmission mode and reflection mode. Each pixel includes a transmission region which uses back light source, and a reflection region which uses ambient light as its light source.
Please refer to FIG. 1. FIG. 1 schematically illustrates a conventional transflective LCD. As shown in FIG. 1, the conventional LCD includes a substrate 10 having reflection regions 12 and transmission regions 14 defined thereon. Each reflection region 12 includes a thin film transistor (TFT) formed therein. The TFT comprises a semiconductor layer including a channel 16, a source electrode 18, a drain electrode 20 and two lightly doped drains (LDDs) 21, a gate insulating layer 22, and a gate electrode 24. The source electrode 18 and the drain electrode 20 are disposed on two opposite side of the channel 16 respectively. One of the LDD 21 is disposed between the source electrode 18 and the channel 16, and the other LDD 21 is between the drain electrode 20 and the channel 16. The gate insulating layer 22 is disposed on the channel 16, the source electrode 18 and the drain electrode 20. The gate electrode 24 is disposed on the gate insulating layer 22 and corresponding to the channel 16.
The gate insulating layer 22 and the gate electrode 24 are covered with a first inter-layer dielectric layer 26. The first inter-layer dielectric layer 26 and the gate insulating layer 22 disposed beneath have two openings respective exposing the source electrode 18 and the drain electrode 20. A data line 28 and a drain pad 30 are disposed on the first inter-layer dielectric layer 26. The data line 28 fills into the opening over the source electrode 18 so as to electrically connect to the source electrode 18; the drain pad 30 fills into the opening over the drain electrode 20 so as to electrically connect to the drain electrode 20. In the reflection region 12, the first inter-layer dielectric layer 26, the data line 28 and the drain pad 30 are covered with a second inter-layer dielectric layer 32. The second inter-layer dielectric layer 32 has an opening exposing the drain pad 30. The second inter-layer dielectric layer 30 and the first inter-layer dielectric layer 26 are covered with a transmission electrode 34, where the transmission electrode 34 is electrically connected to the drain pad 30 and the drain electrode 20 via the opening of the second inter-layer dielectric layer 32. The transmission electrode 34 also extends to the transmission region 14. In addition, a reflection electrode 36 is disposed on the transmission electrode 34 in the reflection region 12, and the reflection electrode 36 is electrically connected to the drain electrode 20 through the transmission electrode 34 and the drain pad 30.
The conventional transflective LCD, however, suffers from the following drawbacks. First, the conventional transflective LCD has to be fabricated by at least eight photolithographic processes to define the semiconductor layer, the source electrode/drain electrode, the LDD, the gate electrode, the first inter-layer dielectric layer, the data line/drain pad, the second inter-layer dielectric layer, the transmission electrode/reflection electrode respectively, and the process step is therefore complicated. In addition, the second inter-layer dielectric layer is formed in the reflection region but not in the transmission region, which generates a height gap between the reflection region and the transmission region. This height gap increases the difficulty in rubbing the alignment patterns, controlling the cell gap, and arranging the spacers in successive liquid crystal process.